So sorry for your loss. Unless you have his logins and passwords, you will need to contact each of the services that he had, contact their support departments, and be prepared to provide documentation to them like the ***** certificate, and proof of your ID and relationship to the account holder. This is difficult for you to jump through these hoops, but at the same time, we would not like it to be too easy for a criminal to change our own accounts, so the companies have procedures to follow.